Effect of die structure on extrusion forming of thin-walled component with I-type longitudinal ribs

The thin-walled component with I-type longitudinal ribs is widely used in aerospace and defense equipment due to its advantage of high-performance and lightweight, yet this complex structure is difficult to manufacture. One method is to form a simple thin-walled tube and I-type longitudinal ribs respectively and then connect them together by welding or riveting. Another method is to form a simple thick-walled tube firstly and then cut out the I-type longitudinal ribs. However, welding or riveting will weaken the component performance and cutting will waste lots of material. In this paper, the extrusion forming process is tried to manufacture the seamless thin-walled components with I-type longitudinal ribs. By FE simulation and experiment of the initial extrusion forming process scheme, it can be found that the metal flow velocities in the thin wall and longitudinal ribs areas are different, which lead to the deformation instability, even producing cracking. To solve the deformation instability, the effects of die structure including the porthole, the baffle-block, and the secondary welding chamber on the metal flow in extrusion process are studied. It reveals that increasing the area of the porthole will increase the metal flow velocity, increasing the height of the baffle-lock will decrease the metal flow velocity, and decreasing the height of the secondary welding chamber will improve the metal flow uniformity. Thus, the velocity uniformity of the metal flow at different position can be controlled in a better level to guarantee stable deformation by selecting appropriate die structure parameters. Finally, an optimized die structure is designed and the extrusion experiment is carried out, which obtain a good forming quality. The research work can provide an important guidance for improving the manufacturing level of thin-walled component with I-type longitudinal ribs.